Neural tube defects in 21st century: Is Northern Ireland changing?
Authors: Tabib Dabir, Fiona Stewart, Nan Hill
Background
Neural tube defects (NTD), which include spina bifida,
anencephaly, and encephalocele, are an important group of severe
birth defects whose prevalence has fallen significantly in past few
decades in many countries. Northern Ireland (NI) is known to have
the highest prevalence of neural tube defects (NTD) in Europe. The
prevalence rate of 60 and 40 per 10,000 births was reported in 70s
and 80s respectively. However no NI data have been published since
then to assess the trend of decline in NTD prevalence as noted in
other previously high prevalent regions of UK and Ireland. The aims
of the study were (1) To describe the current epidemiology of NTD
in Northern Ireland (2) To assess the impact of prenatal diagnosis
on the birth prevalence of spina bifida and anencephaly (3) To
compare the current prevalence, antenatal diagnosis and termination
trend with previously published reports from the province (3) To
compare the current NI data with rest of UK and Europe for the same
period.
Materials and Methods
Total births, all births and terminations of pregnancy affected
with NTD in the province were ascertained for the study period
2000- 2004. The relevant information regarding maternal age, family
history, maternal folate intake, antenatal versus postnatal
diagnosis and genetic investigations was obtained, crosschecked and
analysed. The data was compared with the published figures for the
same period from rest of UK and Ireland and with the data published
by EUROCAT.
Results
Total prevalence rate of 10.24 and birth prevalence rate of 4.66
per 10,000 births was noted for NTD in Northern Ireland. The fall
in total prevalence and birth prevalence of NTD is highly
significant. Eighty four percent cases of neural tube defects were
diagnosed antenatally leading to termination of pregnancy in 30%
and 83% cases of spina bifida and anencephaly respectively.
Contrary to previously published reports we noticed male
predominance in spina bifida cases in our NTD cohort.
Conclusions
This study shows that NI does not have the highest prevalence of
NTD as noted in the past and the prevalence rate is reduced to 1 in
1000 births. This prevalence rate is in keeping with the trend
noted in other UK and Irish centres during the same period. Over
four fifths cases were diagnosed antenatally and the antenatal
diagnosis has made significant impact on the birth prevalence of
neural tube defects.
Clinical Genetics Department, Belfast City Hospital, Lisburn
Road, Belfast, Northern Ireland, UK , BT9 7AB E-mail:
tabib.dabir@belfasttrust.hscni.net
